Hi i had protected sex before 3 weeks, from my best knowledge, the condom didn't break. i'm facing symptoms like pimples and headache (anxiety). hiv??

Too soon to know: HIV would not manifest as pimples at three weeks after exposure. You should get tested for HIV nucleic acid and if the result is negative, repeat the test in 6 months. For good health - Have a diet rich in fresh vegetables, fruits, whole grains, milk and milk products, nuts, beans, legumes, lentils and small amounts of lean meats. Avoid saturated fats. Drink enough water daily, so that your urine is mostly colorless. Exercise at least 150 minutes/week and increase the intensity of exercise gradually. Do not use tobacco, alcohol, weed or street drugs in any form. Practice safe sex, if you have sex.

Not related: Don't believe your symptoms are HIV related but you should consider getting testing for HIV if you are concerned.